A dilatant fluid is a mixture of liquid and particles and behaves as a fluid under slow deformation and as a solid in response to rapid deformation. This nature is utilized in a variety of industrial fields (see Patent Documents 1 to 4).
Recently, the dilatant fluid is used for protecting a fuel cell stack mounted inside fuel cell vehicles (see Patent Document 5). In the fuel cell stack, the dilatant fluid conforms to slow deformation as in the case of cell deflection, to prevent the cells from being further deformed or damaged. On the other hand, when large deformation is applied as in the case of a minor collision, the dilatant fluid behaves as a solid to prevent misalignment of the cell stack. However, the fuel cell stack of Patent Document 5 has the problem that since the dilatant fluid is received in a bag, the dilatant fluid leaks out upon breakage of the bag.
If a solid material like rubber exerts dilatant properties, the problem of Patent Document 5 would be overcome. However, the prior art crosslinked rubber does not always exhibit a high storage elastic modulus at a high strain rate. In order to increase the storage elastic modulus at a high strain rate, the amount of a filler added must be increased. A heavy loading of the filler, however, causes a viscosity buildup to the composition prior to curing, making the composition difficult to handle.